Interpretive Summary: Minimizing contamination in ginned fibers is one of the keys to keep U.S. cotton competitive in global market. Neps, seed coat fragments, and motes are main types of impurities in ginned fibers affecting yarn quality and causing difficulty in dyeing fabrics. Determination of germplasm with good potential performance for reducing neps, seed coat fragments, and motes can identify parents in breeding for genetic improvement of these traits. Crosses were made between elite germplasm and exotic germplasm lines in order to combine desirable genes for these traits into cultivars. Exotic germplasm line SP156 was identified as a good combiner for neps, seed coat fragments, motes, as well as other traits such as lint yield, fiber length, immature fiber content, and short fiber content. Therefore, this germplasm line is an excellent parent in breeding for genetic improvement of both cotton lint yield and fiber quality.

Technical Abstract:
Minimizing neppiness, i.e., neps, seed coat fragments, and motes, in ginned cotton (Gossypium hirsutum L.) fibers is one of the keys to keep U.S. fibers competitive in global market. Forty-eight F2 hybrids derived from crosses between 12 exotic germplasm lines (male parents), i.e., 6 Species Polycross (SP) and 6 John Cotton (JC) lines, and 4 elite germplasm lines (female parents) were evaluated to detect combining ability for the neppiness traits. F2 hybrids and parents were planted at two locations with 4 and 3 replicates each in 2008 and 2009. Neps and seed coat fragments were measured using Advanced Fiber Information System. Significant general combining ability (GCA) effects were observed for most neppiness traits. Additive effects were more important than non-additive effects for neps, seed coat neps (SCN), and motes. Nep count was favorably correlated with short fiber content by number (SFCn) in F2 (r=0.52) and unfavorably correlated with fineness in F2 (r=-0.50). MD15 was the best female parent with negative GCA effects for nep size, SCN size, SCN count, and SFCn. SP156 was the best general combiner with favorable GCA effects for nep count, SCN count, mote count, upper quartile length, SFCn, and immature fiber content with positive GCA effect for lint yield. Results provide evidence for possibility of simultaneous genetic improvement of multiple neppiness traits with lint yield and other fiber properties in Upland cotton using SP156 as parent.